EyeOS has released version 2.0 Beta. "After several months of hard work we're happy to announce the immediate availability of the official release of eyeOS 2.0 Beta. And even more: the new release doesn't come alone but with the brand new eyeOS.org website, which has not ben redesigned for the last 2 years now. eyeOS 2.0 Beta can be downloaded from the new downloads page and tested from a Beta test server in eyeOS.info."

OS = Everything needed in order to make a computer usable by its average user.
OS != A graphical shell that require Linux/Windows/Mac OS X/Other to be run.

Chrome OS is an operating system because you can install it on a blank hard drive, plug said hard drive on a computer and use its function, in an auto-sufficient fashion.
EyeOS is not an operating system because it requires additional software to render a blank machine usable.

As someone said, it may be considered as an operating system layer. But being autosufficient is a necessary condition in order to be labeled an operating system.

That's a good description.
"I believe some books describe an OS as the software that allows other software to interface with the hardware" (or words to that effect) which echoes much of what you've described.

Now while I do believe that where an OS starts and where it stops is a somewhat blurry line these days - what with "integrated" web browsers and other applications, countless variations on a theme (as seen with Linux distros) and powerful graphical shells that are whole environments in themselves.

However that doesn't mean that anything that can launch processes is an operating system.

So I think your post is an excellent description of why EyeOS is not an OS yet Linux is.